BERLIN (AP) — The German government is decrying the seizure of European military observers by pro-Russian militants in eastern Ukraine as an act of "hostage taking" and is calling for their immediate release.

The eight observers, including three German officers, were seized Friday on allegations they were spying for NATO.

A Swedish officer was released Sunday, and German captive Col. Axel Schneider spoke on behalf of the group that same day, stressing at a news conference — under armed guard — that they were on an OSCE diplomatic mission and not spies.

Chancellor Angela Merkel's spokesman Steffen Seibert told reporters on Monday that Germany "strongly condemns this hostage taking" and called for the observers to be released "immediately, unconditionally and unharmed."

He urged Russia to intervene and "clearly distance itself from these acts."